1. Field of the Invention
Embodiments presented herein relate generally to electrical circuits and input/output (“I/O”) interfaces, and, more particularly, to a method and circuit for a low-power, high-gain multistage comparator.
2. Description of Related Art
Electrical circuits and devices that store and transfer data have evolved becoming faster, having larger capacities and transmitting greater amounts of data. With the increased speed, capacity and bandwidth capabilities of electrical circuits and data storage devices, I/O interfaces must be adapted to be compatible with new system and technology requirements. As technologies for electrical circuits, communications and data storage devices have progressed, there has developed a greater need for efficiency, reliability and stability, particularly in the area of I/O interfaces. However, considerations for voltage, current, signal speed, drive strength and power consumption introduce substantial barriers to efficiently receiving and transmitting signals for I/O interfaces. Parameters such as high-gain and low-current gains for differential signal receiving and transmitting are particularly problematic.
Typically, in modern implementations for I/O interfaces, current mirrors are used to generate reference and bias voltages for signal comparator stages by providing voltage values to inverters in a comparator. However, current mirrors are inadequate to provide additional gain and require extra circuitry and power drain (put another way, biased inverters do not overcome barriers for the parameters discussed above (e.g., power consumption and/or signal amplitude)). That is, supplying a reference voltage signal to an inverter stage of a comparator from a current mirror does not improve the gain of the comparator and reduces overall circuit performance/efficiency (e.g., by sinking current and dissipating power) as used state of the art solutions. Digital inverters, such as those formed from an nFET/pFET pair, do not produce gain, and current mirrors use additional circuit power.
Embodiments presented herein eliminate or alleviate the problems inherent in the state of the art described above.